The process of applying roofing or siding shingles to the roof or outside walls of a building is an arduous, time consuming task. Roofers must work on steep surfaces, repeatedly crouching or sitting to position shingles; hammering or stapling the shingles and moving to the next location to be covered, all in frequently high temperatues. Conventionally, the roof or exterior wall to be covered is first provided with some sort of scaffolding or support structure on which the roofers stand to complete the shingle installation. Usually, chalk lines are applied to the roof or exterior wall to provide regular horizontal and vertical reference lines for use in attaching the shingles. As is understood in the art, such reference lines are considered necessary to ensure the laying of regular courses of shingles which provide a neat and uniform exterior appearance for the building. The process of providing the chalk lines is a time consuming one and the subsequent process of individually placing shingles in alignment with the chalk lines; manually holding the shingles in place; fastening the shingles; and then repeating these steps also is quite slow and tiresome.
The prior art discloses a numerous devices which are intended to simplify the process of applying roofing or siding shingles. For example, U.S. Pat. No. 988,808 discloses a roof scaffold including a horizontal alignment bar which may be moved upwardly along the roof surface as the job progresses. Similarly, U.S. Pat. No. 3,842,934 shows a complex type of scaffolding for laying roofing materials on a sloping roof. Although these prior art systems do ease somewhat the task of laying parallel rows of shingles, it is still necessary for the roofer to manually adjust each shingle as it is laid to ensure that succeeding rows of shingles are staggered relative to one anothr in the usual manner. Also, cumbersome equipment must be moved from row to row. Another attempt at providing alignment guides for shingles is disclosed in U.S. PAT. No. 3,110,113 which includes an alignment guide having means attached thereto for orienting a row of shingles to be laid so that they are staggered relative to a previously laid row of shingles. However, the structure of this device is such that it is necessary for the roofer to very carefully insert a plurality of guide elements between the tabs of the shingles of a previously laid row in order to set up the device for laying a new row of shingles. Also, the device is adapted only for use with a single standard shingle.
Prior art devices also fail to account for the fact that even mass-produced shingles will vary in overall length, tab location, thickness and the like from lot to lot or manufacturer to manufacturer. Length and tab location variability of as little as one-fourth inch per shingle can result in a very noticeable, and undesirable, misalignment of shingles where such variations accumulate for long rows of shingles. Variations in shingle thickness can cause the clamps used in some prior art devices to fail to grip their shingles sufficiently or to over compress and damage thicker shingles. Where the grip is too loose, prior art devices fail to hold the required horizontal position, resulting in misalignment. Where the grip is too tight, the protective mineral coating on the shingle may be so damaged as to expose the underfelt to undesirable weathering, to reduce the fire resistance of the shingle or to cause actual leakage.
Thus, it is seen that although the prior art discloses numerous attempts to provide alignment devices which will simplify and speed up the shingling process, there remains a need for an inexpensive durable alignment guide which may be quickly and easily installed in its operating position on most commonly encountered roofs or exterior walls; will accept a plurality of standard roofin and siding strip shingles; will automatically stagger succeeding rows of shingles relative to the previously laid row; and will ensure that succeeding rows of shingles are subsantially parallel.